The present invention relates generally to rotary kilns and the like, and more particularly to a refractory block suitable for installation in the refractory lining of a rotary kiln.
Refractory material lining the interior steel shell of large rotary kilns, such as used in the production of cement and lime, is very difficult to hold in place due to warping of the shell, and is subject to much wear and erosion due to continuous abrasion of the hot materials being processed through the kilns. These conditions are especially prevalent at the discharge end or so-called nose of the kiln. Many rotary kilns employ a plastic refractory nose ring, fixed to the discharge end of the shell, in which extruded refractory material is pounded or rammed over anchors in a steel cylindrical retainer to form a monolithic structure. When a portion of the refractory material becomes worn, it is necessary to replace the entire ring usually with much effort and production downtime. For example, in one typical cement plant the operators required 72 to 80 hours to install a complete plastic refractory nose ring of this type.
Another form of rotary kiln nose ring consists of precast refractory blocks secured to the interior of a steel cylindrical retainer by bolts distributed around the periphery. In a new kiln, securing the blocks to the retainer is usually a simple procedure since everything is in proper alignment. However, with extensive use, the retainer warps and the blocks shift forcing the them out of alignment with the bolts. Replacing individual worn blocks therefore becomes very difficult and time-consuming. In some instances, though only a few blocks may need replacement, it is more cost-effective to replace the entire nose ring, as in the case of the monolithic nose ring, because the unworn blocks have shifted position.